Healthspan vs lifespan: what ageing is, and how much of it you can change

Two numbers, and the gap between them

Lifespan is the number of years you live. Healthspan is the number of years you live free of serious disease, disability and dependence. Global life expectancy has climbed to around 73 years; healthy life expectancy has climbed too, but more slowly, and the gap between the two now averages about nine years worldwide. A 2024 analysis of WHO data across 183 countries (Garmany and Terzic, JAMA Network Open) put it at 9.6 years, and wider in rich countries with long lifespans — the United States sits at roughly 12.

Those nine to twelve years are the problem this whole section exists to shrink. They are usually spent with two or more chronic conditions, declining muscle, poorer sleep and a steadily narrowing life. Nobody is asking for them. The encouraging part of the research is that the gap is not fixed: the people who reach old age in the top of the fitness and metabolic distributions compress it to a few years, and sometimes to months.

So when we say "longevity" on this site we mean healthspan — the years that feel like your own — and every article that follows is about moving one of the levers that the evidence says widens it.

The hallmarks of ageing

In 2013 a group led by Carlos López-Otín published The Hallmarks of Aging in Cell, proposing nine shared biological processes that drive ageing in every tissue. The 2023 update expanded the list to twelve. They are the vocabulary behind most longevity claims, so it helps to know what each one actually means and whether anything is known to move it in a person.

The honest reading of that table: the hallmarks are real, they are connected, and the things that move several of them at once in humans are unglamorous — fitness, muscle, body fat, sleep and not smoking. Most products marketed against a single hallmark have not been shown to change anything you would notice.

How much of ageing is genetic?

Less than people assume. The classic Danish twin studies (Herskind 1996) estimated the heritability of lifespan at about 20–30%. A 2018 analysis of 400 million people in Ancestry family trees (Ruby et al., Genetics) found that once you account for the fact that people marry people like themselves, true heritability is probably under 10%. Genes matter more at the extremes — centenarians do cluster in families — but for the rest of us, how we live explains most of the difference.

The cohort data say the same thing from the other side. In the Nurses' Health Study and the Health Professionals Follow-up Study (Li et al. 2018, Circulation; 123,000 adults followed for decades), five low-risk habits — never smoking, a healthy weight, 30 minutes of daily activity, a decent diet and moderate alcohol — were associated with 14 extra years of life expectancy at age 50 for women and 12 for men, compared with people who had none of them. A follow-up paper showed most of those extra years were disease-free.

The Interheart study (Yusuf et al. 2004, Lancet; 29,972 people in 52 countries) found that nine modifiable factors — abnormal lipids, smoking, hypertension, diabetes, abdominal obesity, psychosocial stress, low fruit and vegetable intake, alcohol and inactivity — accounted for about 90% of the population risk of a first heart attack, in every region and both sexes. The lipid signal was the ApoB/ApoA1 ratio, not total cholesterol.

What is actually modifiable — ranked by the strength of the evidence

Notice what is not in the table: supplements, peptides, NAD infusions, cold plunges. Some of those have a place, and later articles say where. None of them is in the same league as the rows above, and a protocol that starts with them while ignoring the table is a protocol written in the wrong direction.

What to measure

You cannot manage a gap you have not measured. The minimum set that tracks the table above:

• VO2max — a lab test, or a validated field test or watch estimate. Once a year.
• Grip strength with a dynamometer, and a timed chair-stand test. Twice a year.
• Body composition by DEXA: lean mass index and visceral fat, not just weight. Once a year.
• Blood: ApoB, hsCRP, HbA1c, fasting insulin, cystatin C, ferritin, vitamin D, a hormone panel appropriate to your sex and age. The full list is in biomarkers of ageing.
• Sleep: duration and regularity from a wearable, and a screening questionnaire for apnoea if you snore or wake unrefreshed.
• Blood pressure at home, averaged over a week, twice a year.

Everything else — epigenetic clocks, telomere tests, microbiome panels — is interesting and optional. None of it has been shown to change what you should do once the list above is known.

Where peptides and therapies fit

Honestly: downstream of all of the above. A research peptide protocol can support a specific goal — the compounds on the longevity goal page are studied for sleep quality, recovery and body composition, which are three of the levers in the table — but none of them replaces a fitness level, a muscle mass or a metabolic state. The same is true of clinic therapies: sauna has the best cohort data of any of them, and it still sits behind training in every plan we write. The baseline-labs guide explains why the blood work comes first, whatever is layered on top.

Common mistakes

• Optimising lifespan instead of healthspan. A protocol that only chases a longer life ignores the decade that actually needs fixing.
• Starting with the exotic layer. Spending on infusions or compounds before VO2max, strength and body composition have been measured, let alone improved.
• Trusting a single clock. Epigenetic age tests vary by several years between vendors and between weeks. Use them, if at all, as a trend over years, never as a verdict.
• Treating the hallmarks as a shopping list. One product per hallmark is marketing logic, not biology. The levers that matter move several hallmarks at once.
• Assuming your genes have decided. Heritability of lifespan is low. Family history changes which markers to watch; it does not fix the result.